/*
 * Copyright 2001-2004 The Apache Software Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package net.jforum.util.legacy.commons.fileupload;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.Serializable;
import java.io.UnsupportedEncodingException;

/**
 * <p>
 * Low level API for processing file uploads.
 * 
 * <p>
 * This class can be used to process data streams conforming to MIME 'multipart'
 * format as defined in <a href="http://www.ietf.org/rfc/rfc1867.txt">RFC
 * 1867</a>. Arbitrarily large amounts of data in the stream can be processed
 * under constant memory usage.
 * 
 * <p>
 * The format of the stream is defined in the following way:<br>
 * 
 * <code>
 *   multipart-body := preamble 1*encapsulation close-delimiter epilogue<br>
 *   encapsulation := delimiter body CRLF<br>
 *   delimiter := "--" boundary CRLF<br>
 *   close-delimiter := "--" boudary "--"<br>
 *   preamble := &lt;ignore&gt;<br>
 *   epilogue := &lt;ignore&gt;<br>
 *   body := header-part CRLF body-part<br>
 *   header-part := 1*header CRLF<br>
 *   header := header-name ":" header-value<br>
 *   header-name := &lt;printable ascii characters except ":"&gt;<br>
 *   header-value := &lt;any ascii characters except CR & LF&gt;<br>
 *   body-data := &lt;arbitrary data&gt;<br>
 * </code>
 * 
 * <p>
 * Note that body-data can contain another mulipart entity. There is limited
 * support for single pass processing of such nested streams. The nested stream
 * is <strong>required</strong> to have a boundary token of the same length as
 * the parent stream (see {@link #setBoundary(byte[])}).
 * 
 * <p>
 * Here is an example of usage of this class.<br>
 * 
 * <pre>
 *    try {
 *        MultipartStream multipartStream = new MultipartStream(input,
 *                                                              boundary);
 *        boolean nextPart = multipartStream.skipPreamble();
 *        OutputStream output;
 *        while(nextPart) {
 *            header = chunks.readHeader();
 *            // process headers
 *            // create some output stream
 *            multipartStream.readBodyPart(output);
 *            nextPart = multipartStream.readBoundary();
 *        }
 *    } catch(MultipartStream.MalformedStreamException e) {
 *          // the stream failed to follow required syntax
 *    } catch(IOException) {
 *          // a read or write error occurred
 *    }
 * 
 * </pre>
 * 
 * @author <a href="mailto:Rafal.Krzewski@e-point.pl">Rafal Krzewski</a>
 * @author <a href="mailto:martinc@apache.org">Martin Cooper</a>
 * @author Sean C. Sullivan
 * 
 * @version $Id: MultipartStream.java,v 1.4 2007/04/12 02:11:54 rafaelsteil Exp
 *          $
 */
public class MultipartStream {

    // ----------------------------------------------------- Manifest constants

    /**
     * The Carriage Return ASCII character value.
     */
    public static final byte CR = 0x0D;

    /**
     * The Line Feed ASCII character value.
     */
    public static final byte LF = 0x0A;

    /**
     * The dash (-) ASCII character value.
     */
    public static final byte DASH = 0x2D;

    /**
     * The maximum length of <code>header-part</code> that will be processed (10
     * kilobytes = 10240 bytes.).
     */
    public static final int HEADER_PART_SIZE_MAX = 10240;

    /**
     * The default length of the buffer used for processing a request.
     */
    protected static final int DEFAULT_BUFSIZE = 4096;

    /**
     * A byte sequence that marks the end of <code>header-part</code> (
     * <code>CRLFCRLF</code>).
     */
    protected static final byte[] HEADER_SEPARATOR = { CR, LF, CR, LF };

    /**
     * A byte sequence that that follows a delimiter that will be followed by an
     * encapsulation (<code>CRLF</code>).
     */
    protected static final byte[] FIELD_SEPARATOR = { CR, LF };

    /**
     * A byte sequence that that follows a delimiter of the last encapsulation
     * in the stream (<code>--</code>).
     */
    protected static final byte[] STREAM_TERMINATOR = { DASH, DASH };

    // ----------------------------------------------------------- Data members

    /**
     * The input stream from which data is read.
     */
    private InputStream input;

    /**
     * The length of the boundary token plus the leading <code>CRLF--</code>.
     */
    private int boundaryLength;

    /**
     * The amount of data, in bytes, that must be kept in the buffer in order to
     * detect delimiters reliably.
     */
    private int keepRegion;

    /**
     * The byte sequence that partitions the stream.
     */
    private byte[] boundary;

    /**
     * The length of the buffer used for processing the request.
     */
    private int bufSize;

    /**
     * The buffer used for processing the request.
     */
    private byte[] buffer;

    /**
     * The index of first valid character in the buffer. <br>
     * 0 <= head < bufSize
     */
    private int head;

    /**
     * The index of last valid characer in the buffer + 1. <br>
     * 0 <= tail <= bufSize
     */
    private int tail;

    /**
     * The content encoding to use when reading headers.
     */
    private String headerEncoding;

    // ----------------------------------------------------------- Constructors

    /**
     * Default constructor.
     * 
     * @see #MultipartStream(InputStream, byte[], int)
     * @see #MultipartStream(InputStream, byte[])
     * 
     */
    public MultipartStream() {
    }

    /**
     * <p>
     * Constructs a <code>MultipartStream</code> with a custom size buffer.
     * 
     * <p>
     * Note that the buffer must be at least big enough to contain the boundary
     * string, plus 4 characters for CR/LF and double dash, plus at least one
     * byte of data. Too small a buffer size setting will degrade performance.
     * 
     * @param input
     *            The <code>InputStream</code> to serve as a data source.
     * @param boundary
     *            The token used for dividing the stream into
     *            <code>encapsulations</code>.
     * @param bufSize
     *            The size of the buffer to be used, in bytes.
     * 
     * 
     * @see #MultipartStream()
     * @see #MultipartStream(InputStream, byte[])
     * 
     */
    public MultipartStream(InputStream input, byte[] boundary, int bufSize) {
	this.input = input;
	this.bufSize = bufSize;
	this.buffer = new byte[bufSize];

	// We prepend CR/LF to the boundary to chop trailng CR/LF from
	// body-data tokens.
	this.boundary = new byte[boundary.length + 4];
	this.boundaryLength = boundary.length + 4;
	this.keepRegion = boundary.length + 3;
	this.boundary[0] = CR;
	this.boundary[1] = LF;
	this.boundary[2] = DASH;
	this.boundary[3] = DASH;
	System.arraycopy(boundary, 0, this.boundary, 4, boundary.length);

	head = 0;
	tail = 0;
    }

    /**
     * <p>
     * Constructs a <code>MultipartStream</code> with a default size buffer.
     * 
     * @param input
     *            The <code>InputStream</code> to serve as a data source.
     * @param boundary
     *            The token used for dividing the stream into
     *            <code>encapsulations</code>.
     * 
     * @exception IOException
     *                when an error occurs.
     * 
     * @see #MultipartStream()
     * @see #MultipartStream(InputStream, byte[], int)
     * 
     */
    public MultipartStream(InputStream input, byte[] boundary) {
	this(input, boundary, DEFAULT_BUFSIZE);
    }

    // --------------------------------------------------------- Public methods

    /**
     * Retrieves the character encoding used when reading the headers of an
     * individual part. When not specified, or <code>null</code>, the platform
     * default encoding is used.
     * 
     * 
     * @return The encoding used to read part headers.
     */
    public String getHeaderEncoding() {
	return headerEncoding;
    }

    /**
     * Specifies the character encoding to be used when reading the headers of
     * individual parts. When not specified, or <code>null</code>, the platform
     * default encoding is used.
     * 
     * @param encoding
     *            The encoding used to read part headers.
     */
    public void setHeaderEncoding(String encoding) {
	headerEncoding = encoding;
    }

    /**
     * Reads a byte from the <code>buffer</code>, and refills it as necessary.
     * 
     * @return The next byte from the input stream.
     * 
     * @exception IOException
     *                if there is no more data available.
     */
    public byte readByte() throws IOException {
	// Buffer depleted ?
	if (head == tail) {
	    head = 0;
	    // Refill.
	    tail = input.read(buffer, head, bufSize);
	    if (tail == -1) {
		// No more data available.
		throw new IOException("No more data is available");
	    }
	}
	return buffer[head++];
    }

    /**
     * Skips a <code>boundary</code> token, and checks whether more
     * <code>encapsulations</code> are contained in the stream.
     * 
     * @return <code>true</code> if there are more encapsulations in this
     *         stream; <code>false</code> otherwise.
     * 
     * @exception MalformedStreamException
     *                if the stream ends unexpecetedly or fails to follow
     *                required syntax.
     */
    public boolean readBoundary() throws MalformedStreamException {
	byte[] marker = new byte[2];
	boolean nextChunk = false;

	head += boundaryLength;
	try {
	    marker[0] = readByte();
	    if (marker[0] == LF) {
		// Work around IE5 Mac bug with input type=image.
		// Because the boundary delimiter, not including the trailing
		// CRLF, must not appear within any file (RFC 2046, section
		// 5.1.1), we know the missing CR is due to a buggy browser
		// rather than a file containing something similar to a
		// boundary.
		return true;
	    }

	    marker[1] = readByte();
	    if (arrayequals(marker, STREAM_TERMINATOR, 2)) {
		nextChunk = false;
	    } else if (arrayequals(marker, FIELD_SEPARATOR, 2)) {
		nextChunk = true;
	    } else {
		throw new MalformedStreamException(
			"Unexpected characters follow a boundary");
	    }
	} catch (IOException e) {
	    throw new MalformedStreamException("Stream ended unexpectedly");
	}
	return nextChunk;
    }

    /**
     * <p>
     * Changes the boundary token used for partitioning the stream.
     * 
     * <p>
     * This method allows single pass processing of nested multipart streams.
     * 
     * <p>
     * The boundary token of the nested stream is <code>required</code> to be of
     * the same length as the boundary token in parent stream.
     * 
     * <p>
     * Restoring the parent stream boundary token after processing of a nested
     * stream is left to the application.
     * 
     * @param boundary
     *            The boundary to be used for parsing of the nested stream.
     * 
     * @exception IllegalBoundaryException
     *                if the <code>boundary</code> has a different length than
     *                the one being currently parsed.
     */
    public void setBoundary(byte[] boundary) throws IllegalBoundaryException {
	if (boundary.length != boundaryLength - 4) {
	    throw new IllegalBoundaryException(
		    "The length of a boundary token can not be changed");
	}
	System.arraycopy(boundary, 0, this.boundary, 4, boundary.length);
    }

    /**
     * <p>
     * Reads the <code>header-part</code> of the current
     * <code>encapsulation</code>.
     * 
     * <p>
     * Headers are returned verbatim to the input stream, including the trailing
     * <code>CRLF</code> marker. Parsing is left to the application.
     * 
     * <p>
     * <strong>TODO</strong> allow limiting maximum header size to protect
     * against abuse.
     * 
     * @return The <code>header-part</code> of the current encapsulation.
     * 
     * @exception MalformedStreamException
     *                if the stream ends unexpecetedly.
     */
    public String readHeaders() throws MalformedStreamException {
	int i = 0;
	byte[] b = new byte[1];
	// to support multi-byte characters
	ByteArrayOutputStream baos = new ByteArrayOutputStream();
	int sizeMax = HEADER_PART_SIZE_MAX;
	int size = 0;
	while (i < 4) {
	    try {
		b[0] = readByte();
	    } catch (IOException e) {
		throw new MalformedStreamException("Stream ended unexpectedly");
	    }
	    size++;
	    if (b[0] == HEADER_SEPARATOR[i]) {
		i++;
	    } else {
		i = 0;
	    }
	    if (size <= sizeMax) {
		baos.write(b[0]);
	    }
	}

	String headers = null;
	if (headerEncoding != null) {
	    try {
		headers = baos.toString(headerEncoding);
	    } catch (UnsupportedEncodingException e) {
		// Fall back to platform default if specified encoding is not
		// supported.
		headers = baos.toString();
	    }
	} else {
	    headers = baos.toString();
	}

	return headers;
    }

    /**
     * <p>
     * Reads <code>body-data</code> from the current <code>encapsulation</code>
     * and writes its contents into the output <code>Stream</code>.
     * 
     * <p>
     * Arbitrary large amounts of data can be processed by this method using a
     * constant size buffer. (see
     * {@link #MultipartStream(InputStream,byte[],int) constructor}).
     * 
     * @param output
     *            The <code>Stream</code> to write data into.
     * 
     * @return the amount of data written.
     * 
     * @exception MalformedStreamException
     *                if the stream ends unexpectedly.
     * @exception IOException
     *                if an i/o error occurs.
     */
    public int readBodyData(OutputStream output)
	    throws MalformedStreamException, IOException {
	boolean done = false;
	int pad;
	int pos;
	int bytesRead;
	int total = 0;
	while (!done) {
	    // Is boundary token present somewere in the buffer?
	    pos = findSeparator();
	    if (pos != -1) {
		// Write the rest of the data before the boundary.
		output.write(buffer, head, pos - head);
		total += pos - head;
		head = pos;
		done = true;
	    } else {
		// Determine how much data should be kept in the
		// buffer.
		if (tail - head > keepRegion) {
		    pad = keepRegion;
		} else {
		    pad = tail - head;
		}
		// Write out the data belonging to the body-data.
		output.write(buffer, head, tail - head - pad);

		// Move the data to the beginning of the buffer.
		total += tail - head - pad;
		System.arraycopy(buffer, tail - pad, buffer, 0, pad);

		// Refill buffer with new data.
		head = 0;
		bytesRead = input.read(buffer, pad, bufSize - pad);

		// [pprrrrrrr]
		if (bytesRead != -1) {
		    tail = pad + bytesRead;
		} else {
		    // The last pad amount is left in the buffer.
		    // Boundary can't be in there so write out the
		    // data you have and signal an error condition.
		    output.write(buffer, 0, pad);
		    output.flush();
		    total += pad;
		    throw new MalformedStreamException(
			    "Stream ended unexpectedly");
		}
	    }
	}
	output.flush();
	return total;
    }

    /**
     * <p>
     * Reads <code>body-data</code> from the current <code>encapsulation</code>
     * and discards it.
     * 
     * <p>
     * Use this method to skip encapsulations you don't need or don't
     * understand.
     * 
     * @return The amount of data discarded.
     * 
     * @exception MalformedStreamException
     *                if the stream ends unexpectedly.
     * @exception IOException
     *                if an i/o error occurs.
     */
    public int discardBodyData() throws MalformedStreamException, IOException {
	boolean done = false;
	int pad;
	int pos;
	int bytesRead;
	int total = 0;
	while (!done) {
	    // Is boundary token present somewere in the buffer?
	    pos = findSeparator();
	    if (pos != -1) {
		// Write the rest of the data before the boundary.
		total += pos - head;
		head = pos;
		done = true;
	    } else {
		// Determine how much data should be kept in the
		// buffer.
		if (tail - head > keepRegion) {
		    pad = keepRegion;
		} else {
		    pad = tail - head;
		}
		total += tail - head - pad;

		// Move the data to the beginning of the buffer.
		System.arraycopy(buffer, tail - pad, buffer, 0, pad);

		// Refill buffer with new data.
		head = 0;
		bytesRead = input.read(buffer, pad, bufSize - pad);

		// [pprrrrrrr]
		if (bytesRead != -1) {
		    tail = pad + bytesRead;
		} else {
		    // The last pad amount is left in the buffer.
		    // Boundary can't be in there so signal an error
		    // condition.
		    total += pad;
		    throw new MalformedStreamException(
			    "Stream ended unexpectedly");
		}
	    }
	}
	return total;
    }

    /**
     * Finds the beginning of the first <code>encapsulation</code>.
     * 
     * @return <code>true</code> if an <code>encapsulation</code> was found in
     *         the stream.
     * 
     * @exception IOException
     *                if an i/o error occurs.
     */
    public boolean skipPreamble() throws IOException {
	// First delimiter may be not preceeded with a CRLF.
	System.arraycopy(boundary, 2, boundary, 0, boundary.length - 2);
	boundaryLength = boundary.length - 2;
	try {
	    // Discard all data up to the delimiter.
	    discardBodyData();

	    // Read boundary - if succeded, the stream contains an
	    // encapsulation.
	    return readBoundary();
	} catch (MalformedStreamException e) {
	    return false;
	} finally {
	    // Restore delimiter.
	    System.arraycopy(boundary, 0, boundary, 2, boundary.length - 2);
	    boundaryLength = boundary.length;
	    boundary[0] = CR;
	    boundary[1] = LF;
	}
    }

    /**
     * Compares <code>count</code> first bytes in the arrays <code>a</code> and
     * <code>b</code>.
     * 
     * @param a
     *            The first array to compare.
     * @param b
     *            The second array to compare.
     * @param count
     *            How many bytes should be compared.
     * 
     * @return <code>true</code> if <code>count</code> first bytes in arrays
     *         <code>a</code> and <code>b</code> are equal.
     */
    public static boolean arrayequals(byte[] a, byte[] b, int count) {
	for (int i = 0; i < count; i++) {
	    if (a[i] != b[i]) {
		return false;
	    }
	}
	return true;
    }

    /**
     * Searches for a byte of specified value in the <code>buffer</code>,
     * starting at the specified <code>position</code>.
     * 
     * @param value
     *            The value to find.
     * @param pos
     *            The starting position for searching.
     * 
     * @return The position of byte found, counting from beginning of the
     *         <code>buffer</code>, or <code>-1</code> if not found.
     */
    protected int findByte(byte value, int pos) {
	for (int i = pos; i < tail; i++) {
	    if (buffer[i] == value) {
		return i;
	    }
	}

	return -1;
    }

    /**
     * Searches for the <code>boundary</code> in the <code>buffer</code> region
     * delimited by <code>head</code> and <code>tail</code>.
     * 
     * @return The position of the boundary found, counting from the beginning
     *         of the <code>buffer</code>, or <code>-1</code> if not found.
     */
    protected int findSeparator() {
	int first;
	int match = 0;
	int maxpos = tail - boundaryLength;
	for (first = head; (first <= maxpos) && (match != boundaryLength); first++) {
	    first = findByte(boundary[0], first);
	    if (first == -1 || (first > maxpos)) {
		return -1;
	    }
	    for (match = 1; match < boundaryLength; match++) {
		if (buffer[first + match] != boundary[match]) {
		    break;
		}
	    }
	}
	if (match == boundaryLength) {
	    return first - 1;
	}
	return -1;
    }

    /**
     * Returns a string representation of this object.
     * 
     * @return The string representation of this object.
     */
    public String toString() {
	StringBuffer sbTemp = new StringBuffer();
	sbTemp.append("boundary='");
	sbTemp.append(String.valueOf(boundary));
	sbTemp.append("'\nbufSize=");
	sbTemp.append(bufSize);
	return sbTemp.toString();
    }

    /**
     * Thrown to indicate that the input stream fails to follow the required
     * syntax.
     */
    public static class MalformedStreamException extends IOException implements
	    Serializable {
	/**
	 * Constructs a <code>MalformedStreamException</code> with no detail
	 * message.
	 */
	public MalformedStreamException() {
	    super();
	}

	/**
	 * Constructs an <code>MalformedStreamException</code> with the
	 * specified detail message.
	 * 
	 * @param message
	 *            The detail message.
	 */
	public MalformedStreamException(String message) {
	    super(message);
	}
    }

    /**
     * Thrown upon attempt of setting an invalid boundary token.
     */
    public static class IllegalBoundaryException extends IOException implements
	    Serializable {
	/**
	 * Constructs an <code>IllegalBoundaryException</code> with no detail
	 * message.
	 */
	public IllegalBoundaryException() {
	    super();
	}

	/**
	 * Constructs an <code>IllegalBoundaryException</code> with the
	 * specified detail message.
	 * 
	 * @param message
	 *            The detail message.
	 */
	public IllegalBoundaryException(String message) {
	    super(message);
	}
    }

    // ------------------------------------------------------ Debugging methods

    // These are the methods that were used to debug this stuff.
    /*
     * 
     * // Dump data. protected void dump() { System.out.println("01234567890");
     * byte[] temp = new byte[buffer.length]; for(int i=0; i<buffer.length; i++)
     * { if (buffer[i] == 0x0D || buffer[i] == 0x0A) { temp[i] = 0x21; } else {
     * temp[i] = buffer[i]; } } System.out.println(new String(temp)); int i; for
     * (i=0; i<head; i++) System.out.print(" "); System.out.println("h"); for
     * (i=0; i<tail; i++) System.out.print(" "); System.out.println("t");
     * System.out.flush(); }
     * 
     * // Main routine, for testing purposes only. // // @param args A String[]
     * with the command line arguments. // @exception Exception, a generic
     * exception. public static void main( String[] args ) throws Exception {
     * File boundaryFile = new File("boundary.dat"); int boundarySize =
     * (int)boundaryFile.length(); byte[] boundary = new byte[boundarySize];
     * FileInputStream input = new FileInputStream(boundaryFile);
     * input.read(boundary,0,boundarySize);
     * 
     * input = new FileInputStream("multipart.dat"); MultipartStream chunks =
     * new MultipartStream(input, boundary);
     * 
     * int i = 0; String header; OutputStream output; boolean nextChunk =
     * chunks.skipPreamble(); while (nextChunk) { header = chunks.readHeaders();
     * System.out.println("!"+header+"!");
     * System.out.println("wrote part"+i+".dat"); output = new
     * FileOutputStream("part"+(i++)+".dat"); chunks.readBodyData(output);
     * nextChunk = chunks.readBoundary(); } }
     */
}
